Abstract
This paper gathers experimental and theoretical investigations about both the geometry-dependent fracture initiation angle and the fracture strength in VO-notched polymethyl methacrylate (PMMA) specimens under mode I loading conditions. The numerical analyses revealed that despite the application of pure mode I loading on the geometrically symmetric VO-notched samples, the maximum tangential stress occurs at two points symmetrically placed on either side of the notch bisector line. The experimental tests performed on some specimens showed that a crack does not necessarily propagate along the notch bisector line. Stress-based theoretical studies were then carried out to justify the experimental findings. The conventional maximum tangential stress (MTS) criterion gave weak predictions of the fracture. Therefore, the predictions were checked with the generalized MTS (GMTS) criterion by taking into consideration the higher-order stress terms. It was demonstrated that the GMTS criterion predictions have satisfactory consistency with the experimental results of the crack initiation angle and the fracture strength.
Highlights
Brittle fracture is one of the most frequent failure modes in engineering structures and components made of brittle materials such as polymethyl-methacrylate (PMMA), rocks, ceramics, glasses and alloys at low temperatures, in which fracture is unstable and propagates rapidly
In this part of the research, the fracture strength of VO-notched components was studied by considering the generalized MTS (GMTS) criterion, which has been described in the previous subsection
Depending on the geometry parameters of the VO-notched specimen, the crack bifurcation out of the symmetry line occurs in some cases but not in all of them. This was called geometry effects in VO-notched specimens subjected to mode I loading and these effects were studied for different geometry parameters
Summary
Brittle fracture is one of the most frequent failure modes in engineering structures and components made of brittle materials such as polymethyl-methacrylate (PMMA), rocks, ceramics, glasses and alloys at low temperatures, in which fracture is unstable and propagates rapidly. Due to symmetry in the geometry and loading conditions, one expects that under pure mode I loading, brittle fracture takes place from a crack initiated and extended along the notch bisector line It has been experimentally shown for sharp V-notches that in some cases the crack bifurcates (i.e., nucleates at an angle significantly different from the symmetry line [17]). The present study investigates the crack bifurcation phenomenon in the VO-notch problem both experimentally and theoretically and, more importantly, predicts the values of bifurcation angle and its corresponding fracture load for a number of VO-notched specimens with different geometry parameters. The efficiency of the adopted procedures in capturing the geometry effect on the fracture behavior of VO-notched components is assessed and discussed
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